Lionfish continue their upriver march

Below is a repost of a piece by Zack from Abaco Scientist about the the lionfish invasion of the Loxahatchee River in southeastern Florida. I grew up on the Loxahatchee, fishing and boating in it, and I knew every nook and cranny in the map below. The snook fishing was amazing and it wasn’t uncommon to see manatees. There was even a dolphin we used to ride – it was paradise!  But we didn’t have to worry about stepping on lionfish.

A 5? (13 cm) lionfish hovering over a restored oyster reef in the Loxahatchee River (Florida). In the background, you can see a plastic tray trap that we use to collect small organisms from the river’s oyster reefs. Hopefully lionfish won’t become a regular part of these samples.

While we’ve know for a while that invasive lionfish are utilizing estuarine habitats in the Loxahatchee River, Florida (Loxahatchee Lionfish Movements), we never expected to run into one while conducting oyster reef research over four miles from the ocean.

If it weren’t for the huge amount of time we spent running around the Loxahatchee River during the summer of 2010 while working on a large-scale oyster reef restoration project, we probably wouldn’t have ever discovered lionfish lurking in the estuary.  That said, we never actually expected to find lionfish living AT our oyster reef study sites.  We’ve always thought that salinity would be too low and turbidity too high in this part of the river to sustain a fish that is typically associated with crystal clear coral reef habitats.

Last week, while sampling a restored oyster reef 4.1 miles (6.6 km) upriver from the ocean, I was shocked to find a subadult lionfish taking shelter directly behind one of our benthic tray traps.  This is almost three-quarters of a mile further upstream than we had previously observed lionfish in the system.  When we first discovered lionfish in the upper reaches of the Loxahatchee estuary, we believed that they were living in a “salt wedge,” a dense layer of full-strength seawater that is commonly found along the bottom of estuaries.  However, the salinity where I found the lionfish last week was only 8 parts per thousand, less than one-fourth the salinity of sea water.  Although salinity tolerance has not been identified for lionfish, this value is surprisingly low (and as far as I can tell, the lowest salinity that wild lionfish have been documented in).  What’s more, the layer of 8 ppt “slightly salty” water only extended about 3? above the oyster reef, above which, salinity quickly dropped to zero (freshwater inflow is currently high, as we are in the middle of Florida’s wet season).  This discovery suggests that lionfish may be able to inhabit estuaries that had previously been considered “too fresh” for the species to survive.  We will continue to keep our eyes open for additional lionfish on the Loxahatchee’s oyster reefs during future sampling dates.

The new lionfish sighting at the restored oyster reef was 3/4 mile further upstream than our previous “upstream limit” (point A) for lionfish in the system (adapted from Jud et al. 201

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